GROUP C – Case study no.4Dr. Nadezda BAGRETS (Karlsruhe Institute of Technology)Dr. Andrea CORNACCHINI (CERN EN Dept.)Mr. Miguel FERNANDES (CERN BE Dept.)Dr. Friedrich LACKNER (CERN TE Dept.)Mr. Shoubo HE (Inst. of Modern Physics - Chinese A. Of Sc.)

Case study no.4

MB.B8R/L

MB.B11R/L

5.5 m Nb3Sn 5.5 m Nb3Sn3 m Collim.

14.3 m Nb-Ti

∫BdL = 119.2 Tm @ Inom = 11.85 kAwith 20 % margin

GOAL:

Design a Nb3Sn superconducting dipole with an 60 mm aperture and a operational field (80% of Iss) at 1.9 K of 11 T.

New collimators to deal with increased beam intensity, energy and ion losses

Cable dimensioning

w t

Bss=Bop / 0,8 = 13,75 T

Aperture = 60mm r = 30mm

Cable geometryStrand diameter 0,75 mmNumber of strands 40Cu to SC ratio 1,5Width 15mmMid thickness 1.39Insulation thickness 15%“Pitch” angle 15.39°Keystone angle 0.64Filling factor 0.273

Short sample solution

Short sample solution

jsc_ss 2560 A/mm2

jo_ss 650 A/mm2

Iss 13.5 kABpeak_ss 13.75 T

Operational condition & marginsoperational cond. (80% Iss ) jsc_op 2114 A/mm2

jo_op 530 A/mm2

Iop 10.8 kABpeak_op 11T

Margins

SC:jop/ jC 0.42Bop/ BC 0.73

overall:jop/ jC 0.47Bop/ BC 0.73

T 4.9 K

Comparison NbTi

It’s not possible to obtain

Bss > 13 T

Bop > 10T (with a reasonable margin)

using NbTi cables

Lay out

Using one wedge, it’s possible to eliminate the B3, B5 and B7 unwanted multipole terms.A possible solution is 48° 60° 72°

Using more wedges, we can eliminate more multipole terms and have a better field quality. This is the real case.

Forces and stressesWe assume:• Uniform j0=530 A/mm2 is the cross-section plane⊥• Inner (outer) radius of the coils = a1 (a2)• Angle = 60º• No iron

Fy

Fx

Fx = 2424 kN/m

Fy = - 2155 kN/m

Accumulate stress on the coil midplane

σ = Fx/w = 80.8 MPa

Colliers and Iron yokeWith 90% of Iss B = 12.4T

For collars we can use as a reference other high field magnets.Thickness of collar = 30 mm

tiron = 186 mm

We can assume the internal radius of the shrinking cylinder as the result of the sum of:D/2 + r + w + tcollar + tiron = 380 mm

D

tshell = 12 mm

Additional questionsCompound Year Tc Bc2(0) ξ Bi2Sr2Ca1Cu2O8 1989 94 > 100a 1 - 2 YBa2Cu3O7 1988 92 > 100a 1 - 2

Bi-2212: Round wires. Future accelerators at >20T. Problem: mechanical stability. No solution yet for enhancing the mechanical reinforcementYBCO: Tapes. Cables, Current limiters, Wind generators. Main problems: costs, limited lengths: Commercially available: < 500 m SuperPower, USA < 500 m at Fujikura, Japan

Assembly procedure: high pre-stress vs. low pre-stress

High temperature superconductor: YBCO vs. Bi2212

Superconducting coil design: block vs. cosΘBlock coil (HD2, HD3, Fresca2)Cable is not keystoned, perpendicular to the midplaneEnds are wound in the easy side, but must be flared to make space for aperture (bend in the hard direction)Internal structure to support the coil neededRatio central field/current density is 12%less than a cosΘ with the same quantity of cable: less effective than cos thetaBlock design is interesting and has good properties but needs more experience

Support structures: collar-based vs. shell-based

The pre-stress avoids the appearance of tensile stresses and limits the movement of the conductors.LHC corrector sextupoles (MCS) Learning curve was poor in free conditions and training was optimal with low pre-stress and around 30 MPa. Degradation was observed for high pre-stress (above 40 MPa) Finally, nominal pre-stress for series production was 30 MPa.

All the collared magnets are characterized by significant coil pre-stress losses: the coil reaches the maximum compression (about 100 MPa) during the collaring operation, but after cool-down the residual prestress is of about 30-40 MPa. BLADDERS and ALUMINIUM THICK SHELL: Initial pre-compression is provided by waterpressurized bladders and locked by keys. After cool-down the coil pre-stress increases due to the high thermal contraction of the aluminum shell.

GROUP C – Case study no.4

Dr. Nadezda BAGRETS (Karlsruhe Institute of Technology)

Dr. Andrea CORNACCHINI (CERN EN Dept.)

Mr. Miguel FERNANDES (CERN BE Dept.)

Dr. Friedrich LACKNER (CERN TE Dept.)

Mr. Shoubo HE (Inst. of Modern Physics - Chinese A. Of Sc.)

Thank you for your attention.